A C-130 tanker plane that crashed and killed all three Americans on board while fighting fires in Australia in 2020 likely stalled when flying in hazardous conditions after making a fire retardant drop, investigators said in a final report on Monday.
There is no evidence that the crew was told a smaller lead aircraft called a "birddog" initially assigned to support the C-130 had declined the mission due to weather-related safety concerns, highlighting a lack of information sharing that may have contributed to the crash, the Australian Transport Safety Bureau (ATSB) said.
"We do know that the use of large air tankers in Australia is relatively new," ATSB Chief Commissioner Angus Mitchell told reporters. "And those policies perhaps haven't been as mature as they've been in other jurisdictions that have used them," he added, citing the US as being more advanced.
The Lockheed Martin Corp C-130 operated by private Canadian firm Coulson Aviation under contract to the New South Wales Rural Fire Service (RFS) was the biggest civilian plane by size to crash in Australia.
The January 2020 accident occurred during the country's worst fire season on record when RFS had up to 130 aircraft a day working to put out fires.
Coulson did not provide a pre-flight risk assessment tool for its firefighting large air tanker crews, ATSB said, while RFS had limited policies for aerial supervision requirements and no procedures for deploying tankers without aerial supervision.
Coulson has taken pro-active steps to improve safety in response to the accident, including the introduction of a pre-flight risk assessment tool and new windshear management procedures and training, though it has declined a recommendation to install windshear detection systems, Mitchell said.
Coulson did not respond immediately to a request for comment. In the final report the operator said it did not believe windshear detection systems would improve safety.
RFS Commissioner Rob Rogers said in a statement that work was underway to put better systems in place ahead of the coming fire season, including establishing a manual process for notifying pilots when others have rejected tasks due to poor conditions.
The C-130 crash killed US military veterans Captain Ian H McBeth, 44, of Great Falls, Montana, First Officer Paul Clyde Hudson, 42, of Buckeye, Arizona, and Flight Engineer Rick DeMorgan Jr, 43, of Navarre, Florida.
The three US firefighters were part of a multi-national team helping Australia combat devastating bushfires.
The cockpit voice recorder was recovered but investigators said the data was not useful because all of the audio was from a flight that was operated in the US in 2019.
The aircraft had been based there before coming to Australia during a bushfire season that killed 33 people, charred nearly 12 million hectares (29.7 million acres) of land and wreaked billions of dollars in damage.